The field of electrosurgery includes a number of loosely related surgical techniques which have in common the application of electrical energy to modify the structure or integrity of patient tissue. Electrosurgical procedures usually operate through the application of very high frequency currents to cut or ablate tissue structures, where the operation can be monopolar or bipolar. Monopolar techniques rely on a separate electrode for the return of RF current that is placed away from the surgical site on the body of the patient, and where the surgical device defines only a single electrode pole that provides the surgical effect. Bipolar devices comprise both electrodes for the application of current between their surfaces.
Electrosurgical procedures and techniques are particularly advantageous as they generally reduce patient bleeding and trauma associated with cutting operations. Additionally, electrosurgical ablation procedures, where tissue surfaces and volume may be reshaped, is not easily duplicated through other treatment modalities.
Generally, radiofrequency (RF) energy is extensively used during arthroscopic procedures because it provides efficient tissue resection and coagulation and relatively easy access to the target tissues through a portal or cannula. Arthroscopic procedures, laproscopic procedures, and the like are often conducted in confined areas such as the synovial sac of the knee or similar body enclosures in the presence of a conductive medium such as an electrically conductive fluid (e.g., saline). However, a challenge with the surgical use of RF energy in confined spaces is that an electrode on the electrosurgical instrument is more likely to come into accidental contact or be placed in close proximity to a low impedance object, such as a metallic endoscope or a soft tissue implant or anchor. When an electrosurgical active electrode is placed in the proximity of metallic objects, there is a high concentration of the electrical field around the metal, and therefore the electrical field can easily exceed the medium, and generate an arc. Especially in cases when the electrical field created by the voltage exceeds the dielectric strength of this medium, an arc discharge plasma (or thermal plasma) may be formed with temperatures usually exceeding 1,500° C. when high frequency voltage is generated across the conductive medium. The high temperature generated by the arc, combined with the shock wave generated by the discharge plasma, can damage tissue, soft tissue implants, or other equipment like crystal lenses of an endoscope. Standard electrosurgical systems used in arthroscopic surgery or other types of surgery may have circuitry that detects high currents associated with arcs, and can be configured to interrupt the high frequency output very rapidly in order to mitigate any potential damage caused by the arc. However, in order to completely remove the risk of arcing and the resultant damage, the high currents associated with a potential arc needs to be dissipated before it is detected. Without such dissipation of the current, an arc may still form, even if only for a very short time (a few hundred nano seconds to several micro seconds, or even sometimes milliseconds) bring forth a potential risk of damaging the RF generator, the endoscope, the surrounding tissue, and any other adjacent tissue implant or surgical equipment.
Previous attempts to mitigate these damaging effects have included limiting the power output of the RF generator and measuring the current periodically to check for acceptable levels. These solutions may be effective to stop an arc once it has occurred but they do not predict or detect the possibility of an arc prior to the arc occurring. Furthermore, over-limiting the power output of the generator reduces the rate of the surgical effect, which is often unacceptable or an annoyance from a clinical perspective. An improved system and method to more accurately predict non-preferable conditions such as arcing to adjacent metallic instruments, accommodating for local temperatures and wear of the instrument is therefore desired.